Need some advice about a structure problem

Question

Me and my team will develop some applications that will communicate with other, this application will work basically like this: A front-end application built with react that communicates with an API. The way that this API will work is: each one of our clients will have an individual database, their users will access our front-end app, this app will locate in a Database that contains the information of, what is their enterprise and will return some connection information for them. After this, each user will have the information of what is their enterprise, and our API will take this info and connect in the database and take the data. My questions are that I don't know the best way to do this (instantiate a datasource in each request and disconnect after || after a user of enterprise x connects, I will make this connection open while are active users on that enterprise || other solution)? And I'm wrong trying to use lb4 for this scenario?

Answer 1

My situation is similar to yours, my team is using `Mongodb` 4.x and I assume you are using it.

Trouble

According to my understanding, your trouble is

• you need to dynamically use different DataSource in different requests.
• The current DataSource address is unchanged after instantiation.

Solution with Mongodb

You need to create a class extends with juggler.DataSource that can dynamically switch databases each time, then inject this class into each controller.

• loopback-datasource-juggler/types/datasource.d.ts

export declare class DataSource extends EventEmitter {

  ...

  connector?: Connector; // <= can access `Mongodb Client` object

• create class extends with juggler.DataSource

export class MyClient extends juggler.DataSource {

    constructor(
        @config()
        settings: Config = config
    ) {
        super(settings);
    }

    public async db(dbName: string): Promise<Database> {
        if (!this.connected) await this.connect();
        // return the `Mongodb DB` object
        return this.connector!.client.db(dbName);
    }

}

• inject MyClient class and use it in controller

export class TestController {

    constructor(
        @inject('my-client')
        private myClient: MyClient,
    ) { }

    @post('/test')
    async test(){
        let db = await this.myClient.db('db-name');
        let col = db.collection('col-name');
        // ...
    }

}